A/F not cycling, stumbly idle, cause found

Aphex · 05-11-2002, 06:42 PM

Hey, this is for a few other people who had the same problem as me, the car would have a very bad idle and the A/F guage would not cycle at idle.

well i pulled the code today and it was the O2 sensor

but the code was for Bank1, sensor 2

however selecting to check the signals on each of the sensors
Bank 1 sensor 2 gives back readings
whereas selecting bank 1 sensor 1 gives an error back saying that it is receiving no signal. pulled the plug for the front O2 sensor now bank 1 sensor 1 reads a constant voltage either 3.8V or .38V I don't remember, plug it back in and it immediately drops down to 0V, and returns an error.

so do I get a new one? is it possible to try to "clean" it? my car used to backfire quite a bit so I wonder if this was the cause of the failure. also the sensor was cross threaded from the factory, so it's not even completely in it's bung, maybe I should just cut my losses and get a new one, what is everybody's opinion?

eli

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Aphex · 05-13-2002, 02:15 AM

some new questions that I've been thinking about

my A/F guage is tied into the front O2 sensor, at idle it's not even on the chart, which it shouldn't since it gives 0V and no data to the ECU, however at cruise and acceleration it does give a reading, so what the hell is going on here? is it the O2 sensor? or something else?

thanks
eli

giulio · 05-13-2002, 09:14 AM

you should still get readings from your front o2 at idle. it should cycle. constant zero V is definitely not right. If it gives a reading while cruising, it might be working fine. Could be something else that is causing a lean condition at idle.

I still have a little bit of idle problems. Usually when i first start the car. It starts at 1200 or so as usual, then drops down and dies.
I was getting a CEL and pulled the code - idle vacuum leak. Since I removed the supercharger to change the clutch slave cyl, i assumed i jerked something loose. It turns out that I didn't let the seal set overnight when I put the s/c back on.
So I redid that, but still had problems. No CEL light though, which means no readable leak. It looks like it was my throttle body. It's attached to the beginning of the s/c kit, right next to the passenger's strut. From moving it around the cable flexes differently and changes the % of throttle at idle. The butterfly wasnt closed enough at 0%. Although the TPS was still reading 0!
Too much air was going in, but the tps was still reading 0%. I'm assuming that at idle the ecu doesnt pay attention to the mass or o2 since not enough volume is going through either. "0% throttle...ok that means little to no fuel..." and it dies.
So after fixing that, it's much better. It still drops to 400, but then catches itself finally. It always did that though... better than stalling at a red light =)
After catching itself it stays at 700 smoothly. It drops to 400 at starting, or when i put in the clutch to stop at a light/sign.

So... check that out. couldnt hurt.
g

ColinL · 05-15-2002, 09:50 AM

I'd get a new front oxygen sensor. Might try to see if a generic bosche part from Autozone is a) available and b) cheaper than Subaru's part.

05-11-2002, 06:42 PM	#1
Aphex Scooby Specialist Member#: 146 Join Date: Aug 1999 Location: Wahcheeta, KS Vehicle: '05 Legacy GT Silver	A/F not cycling, stumbly idle, cause found Hey, this is for a few other people who had the same problem as me, the car would have a very bad idle and the A/F guage would not cycle at idle. well i pulled the code today and it was the O2 sensor but the code was for Bank1, sensor 2 however selecting to check the signals on each of the sensors Bank 1 sensor 2 gives back readings whereas selecting bank 1 sensor 1 gives an error back saying that it is receiving no signal. pulled the plug for the front O2 sensor now bank 1 sensor 1 reads a constant voltage either 3.8V or .38V I don't remember, plug it back in and it immediately drops down to 0V, and returns an error. so do I get a new one? is it possible to try to "clean" it? my car used to backfire quite a bit so I wonder if this was the cause of the failure. also the sensor was cross threaded from the factory, so it's not even completely in it's bung, maybe I should just cut my losses and get a new one, what is everybody's opinion? eli * Registered users of the site do not see these ads.

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05-13-2002, 02:15 AM	#2
Aphex Scooby Specialist Member#: 146 Join Date: Aug 1999 Location: Wahcheeta, KS Vehicle: '05 Legacy GT Silver	some new questions that I've been thinking about my A/F guage is tied into the front O2 sensor, at idle it's not even on the chart, which it shouldn't since it gives 0V and no data to the ECU, however at cruise and acceleration it does give a reading, so what the hell is going on here? is it the O2 sensor? or something else? thanks eli

05-13-2002, 09:14 AM	#3
giulio Scooby Newbie Member#: 16040 Join Date: Mar 2002 Location: NY USA Vehicle: 1998 Impreza RS Supercharged	you should still get readings from your front o2 at idle. it should cycle. constant zero V is definitely not right. If it gives a reading while cruising, it might be working fine. Could be something else that is causing a lean condition at idle. I still have a little bit of idle problems. Usually when i first start the car. It starts at 1200 or so as usual, then drops down and dies. I was getting a CEL and pulled the code - idle vacuum leak. Since I removed the supercharger to change the clutch slave cyl, i assumed i jerked something loose. It turns out that I didn't let the seal set overnight when I put the s/c back on. So I redid that, but still had problems. No CEL light though, which means no readable leak. It looks like it was my throttle body. It's attached to the beginning of the s/c kit, right next to the passenger's strut. From moving it around the cable flexes differently and changes the % of throttle at idle. The butterfly wasnt closed enough at 0%. Although the TPS was still reading 0! Too much air was going in, but the tps was still reading 0%. I'm assuming that at idle the ecu doesnt pay attention to the mass or o2 since not enough volume is going through either. "0% throttle...ok that means little to no fuel..." and it dies. So after fixing that, it's much better. It still drops to 400, but then catches itself finally. It always did that though... better than stalling at a red light =) After catching itself it stays at 700 smoothly. It drops to 400 at starting, or when i put in the clutch to stop at a light/sign. So... check that out. couldnt hurt. g

05-15-2002, 09:50 AM	#4
ColinL Scooby Guru Member#: 114 Join Date: Jul 1999 Chapter/Region: MWSOC Location: Wichita, KS and Whoring, OT Vehicle: '03 Evo, Rice White '01 Erion CBR 929	I'd get a new front oxygen sensor. Might try to see if a generic bosche part from Autozone is a) available and b) cheaper than Subaru's part.